Method for the manufacture of a tube

Abstract

A method for the manufacture of a tube (10) containing a plastic material is proposed. The plastic material is melted in an extruder (3) so that a plastic melt is obtained, wherein the extruder (3) includes a passage (5). A conveyor (4) is arranged in the passage (5). The passage (5) has a first end (6), wherein the plastic material is introduced downstream of the first end (6) into the passage (5). The plastic material is conveyed through the passage (5, 35) and is converted into a plastic melt. The passage (5) has a second end (7), wherein the plastic melt is directed through the passage (5) into a forming tool (8). The tube (10) is produced by means of the forming tool (8), wherein the tube (10) leaves the passage (5) at the second end (7), wherein the tube (10) leaves the passage (5) on the second end (7). The plastic melt is guided through a cooling device (9), wherein the cooling device (9) comprises a cooling element (19) and a mixing element (40, 41), which is arranged in the interior of the passage (5, 35), wherein the plastic melt flows around the cooling element (19, 49) and the mixing element (40, 41), so that the plastic melt is cooled through the cooling element (19, 49) and the plastic melt is mixed by the mixing element (40, 41).

Claims

1. A method for the manufacture of a tube containing a plastic material, wherein the plastic material is melted in an extruder so that a plastic melt is obtained, wherein the extruder includes a passage, a conveyor is arranged in the passage, wherein the passage has a first end, wherein the plastic material is introduced downstream of the first end into the passage, wherein the plastic material is conveyed through the passage and is converted into a plastic melt, wherein the passage has a second end, wherein the plastic melt is directed through the passage into a forming tool, wherein the tube is produced by means of the forming tool, wherein the tube leaves the passage at the second end, wherein the passage in the forming tool includes a mandrel, so that the plastic melt flows from the passage into an annular passage arranged in the forming tool, wherein the annular passage is arranged around the mandrel, wherein the plastic melt is guided through a cooling device, wherein the cooling device a cooling element and a mixing element, which is arranged in the interior of the passage, wherein the plastic melt flows around the cooling element and the mixing element, so that the plastic melt is cooled through the cooling element and the plastic melt is mixed by the mixing element, wherein the cooling element is arranged at least partially within the mixing element.

2. The method according to claim 1, wherein the mixing element or the cooling element comprises a plurality of web elements.

3. The method according to claim 2, wherein the web elements are arranged crosswise to each other.

4. The method according to claim 2, wherein at least a part of the web elements includes a cooling passage.

5. The method according to claim 1, wherein the tube has a wall thickness of at least 3 mm.

6. The method according to claim 1, wherein the tube has an outer diameter of at least 100 mm.

7. The method according to claim 1, wherein the maximum temperature of the plastic melt differs from the minimum temperature of the plastic melt by not more than 10 degrees, so that the plastic melt downstream of the cooling device is homogenized over the flow cross section.

8. The method according to claim 1, wherein the tube comprises at least two layers.

9. The method according to claim 8, wherein each of the layers which comprises at least 10% by weight of the plastic melt is cooled by means of a cooling device.

10. The method according to claim 8, wherein each of the layers is produced by a respective extruder, wherein each of the layers is guided through a separate passage.

11. The method according to claim 1, wherein the conveyor comprises an extruder screw, which is arranged in the passage.

12. The method according to claim 1, wherein the passage includes a first passage portion containing the conveyor, wherein the passage contains a second passage portion which adjoins the first passage portion, wherein the passage contains a third passage portion adjoining the second passage portion, wherein the third passage portion contains the forming tool.

13. The method of claim 12, wherein the cooling device is arranged in the second passage portion, such that the plastic melt in the second passage portion passes through the cooling device.

14. The method according to claim 1, wherein the plastic material contains at least one element from the group consisting of polyethylene or polypropylene.

15. The method according to claim 14, wherein the percentage of polyethylene or polypropylene is at least 50% by weight.

16. The method according to claim 1, wherein the cooling device is arranged upstream of the forming tool.

17. A method for the manufacture of a tube containing a plastic material, said method comprising the steps of melting a mass of plastic material within a passage of an extruder to obtain a plastic melt; guiding the plastic melt through a cooling element within said passage to cool the plastic melt and a mixing element within said passage to mix the cooling plastic melt and wherein the cooling element is arranged at least partially within the mixing element; and thereafter directing the plastic melt through said passage and annularly between a mandrel within said passage and said passage to form a tube for passage from an exit end of said passage.

18. A method as set forth in claim 17 wherein said mandrel is concentrically spaced within said passage to form a tube with a thickness of at least 3 mm.

19. A method as set forth in claim 17 wherein said passage is of a diameter to form a tube with an outer diameter of at least 100 mm.

20. A method as set forth in claim 17 wherein said step of melting and said cooling element maintain a temperature differential of not more than 10 degrees C. between the maximum temperature of said melt and the minimum temperature of said melt,

21. A method for the manufacture of a tube containing a plastic material, said method comprising the steps of melting a first mass of plastic material within a passage of a first extruder to obtain a first plastic melt; guiding the first plastic melt through a cooling element within said passage to cool the plastic melt and a mixing element within said passage to mix the cooling plastic melt and wherein the cooling element is arranged at least partially within the mixing element; thereafter directing the first plastic melt through said passage and annularly between a mandrel within said passage and said passage to form a first tube for passage from an exit end of said passage; melting a second mass of plastic material within a passage of a second extruder to obtain a second plastic melt; guiding the second plastic melt through a cooling element within said passage of said second extruder to cool the second plastic melt and a mixing element within said passage to mix the second cooling plastic melt and wherein the cooling element is arranged at least partially within the mixing element; thereafter directing the second plastic melt from an exit end of said second extruder spaced annularly about said exit end of said passage of said first extruder and onto said first tube to form a multilayer tube.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The method and device according to the invention will now be illustrated with reference to some embodiments. It is shown in

[0036] FIG. 1 a device for performing the method according to a first embodiment,

[0037] FIG. 2 a device for performing the method according to a second embodiment.

DETAILED DESCRIPTION

[0038] FIG. 1 shows a device 1 for manufacturing a tube 10 made of plastic material, comprising a plastic material container 2 for receiving the plastic material, an extruder 3, wherein the extruder 3 includes a conveyor 4, for example an extruder screw or a piston, which is arranged in a passage 5. The passage 5 has a first end 6, wherein the plastic material is contained in the passage 5 downstream of the first end 6. The plastic material container 2 is connectable via a supply line to the passage 5 or connected thereto. There may be provided a plurality of plastic material containers 2 for various plastics materials. Also, containers for additives, propellants or the like may optionally be provided. The passage 5 contains a heat supply device, so that the plastic material in the passage 5 is convertible to a plastic melt. The heat supply device may include a heater, which is not shown in the drawing. The extruder screw may be formed as a heat supply device or contain a heat supply device.

[0039] The passage 5 has a second end 7, wherein the passage 5 forms a connection for the plastic melt from the extruder 3 to a forming tool 8. The forming tool 8 includes an annular passage 18 for producing the tube 10 from the plastic melt. The annular passage 18 extends to the second end 7, wherein the second end 7 includes an opening for the discharge of the plastic melt from the forming tool 8. A cooling device 9 is arranged in the passage 5 upstream of the forming tool 8, wherein the cooling device 9 includes a cooling element 19 and a mixing element 40 which is arranged in the interior of the passage 5, so that the plastic melt flows around the cooling element 19 and the mixing element 40 in the operating state such that a mixing of the plastic melt can take place by the mixing element 40 and a cooling of the plastic melt by the cooling element 19. According to an embodiment, the tube 10 has an outer diameter of at least 100 mm. The tube 10 may have a wall thickness of at least 3 mm. According to an embodiment, the tube 10 has an outer diameter of at least 200 mm. The tube 10 may have a wall thickness of at least 20 mm. The plastic melt can flow around the cooling element 19 and the mixing element 40, if it is arranged such that it projects at least partially into the core flow of the plastic melt. In addition, the cooling element 19 and the mixing element 40 may also be configured such that the wall flow can be cooled by the cooling element 19. In particular, the mixing element 40 may include a guide element to mix the wall flow with the core flow.

[0040] According to an embodiment, the passage 5 has a first passage portion 15, which contains the conveyor 4. The passage 5 has a second passage portion 20, which adjoins the first passage portion 15. The passage 5 has a third passage portion 25, which adjoins the second passage portion 20, the third passage portion 25 containing the forming tool 8. In particular, the cooling device 9 may be arranged in the second passage portion 20. According to an embodiment, a plurality of cooling devices 9 may be provided. The cooling devices 9 can be arranged in a parallel arrangement or in a serial arrangement, which is not shown in the drawing in FIG. 1.

[0041] The cooling device 9 may contain a static mixer or be designed as a static mixer. In particular, the cooling element 19 may be at least partially formed as the mixing element 40.

[0042] The cooling element 19 and the mixing element 40 may form a unit. A plurality of cooling elements 19 or mixing elements 40 may be provided. The cooling element 19 or the mixing element 40 may be formed as a web element. The cooling element 19 or at least a part of the cooling elements may include a passage through which a cooling fluid flows.

[0043] According to the embodiment of a device 30 shown in FIG. 2, the tube 10 may include a plurality of layers. FIG. 2 shows a device 30 for producing a tube 10 made of plastic material, comprising a plastic material container 2, 32 for receiving the plastic material, a first and a second extruder 3, 33. The first and second extruder 3, 33 each contain a conveyor 4, 34, for example, an extruder screw or a piston, which is arranged in each case in a first or second passage 5, 35. The first passage 5 has a first end 6, the second passage 35 has a first end 36, wherein the plastic material is included downstream of the corresponding first end 6, 36 in the passage 5, 35. Each of the first or second passages 5, 35 may include a heat supply device, so that the plastic material in the corresponding passage 5, 35 is convertible to a plastic melt. The heat supply device may include a heater, which is not shown in the drawing. Each of the passages 5, 35 have a second end 7, 37 each, wherein the first passage 5 and the second passage 35 each form a connection for the plastic melt from the first and second extruder 3, 33 to form a forming tool 8. The forming tool 8 includes a first annular passage 18 and a second annular passage 38 for the manufacture of the tube 30 from the plastic melt.

[0044] The first annular passage 18 extends to the second end 7, wherein the second end 7 includes an opening for the discharge of the plastic melt from the forming tool 8. The second annular passage 38 extends to the second end 37, wherein the second end 37 includes an opening for the discharge of the plastic melt from the forming tool 8. Upstream of the forming tool 8, a first cooling device 9 is arranged in the first passage 5 and a second cooling device 39 in the second passage 35, wherein the first cooling device 9 includes a first cooling element 19 and a first mixing element 40, which is arranged in the interior of the first passage 5 in that the plastic melt flows around the first cooling element 19 and the first mixing element 40 in the operating state, so that the plastic melt is mixed by the first mixing element 40. A second cooling device 39 is arranged in the second passage 35, wherein the second cooling device 39 includes a second cooling element 49 and a second mixing element 41, which is arranged in the interior of the second passage 35, so that the plastic melt flows around the second mixing element 41 and the second cooling element 49 in the operating state, so that the plastic melt is mixed by the second mixing element 41. According to an embodiment, the tube 30 has an outer diameter of at least 100 mm. The tube 30 may have a wall thickness of at least 3 mm. According to an embodiment, the tube 30 has an outer diameter of at least 200 mm. The tube 30 may have a wall thickness of at least 20 mm. The plastic melt can flow around by each of the first or second cooling elements 19, 49, if it is arranged such that it projects into the core flow of the plastic melt. In addition, each of the first or second cooling elements 19, 49 may also be configured such that the wall flow can be cooled by the corresponding cooling element 19, 49. In particular, the mixing elements 40, 41 may include a guide element to mix the wall flow with the core flow.

[0045] According to an embodiment, the second passage 35 has a first passage portion 45, which contains the conveyor 34. The second passage 35 has a second passage portion 50, which adjoins the first passage portion 45. The second passage 35 has a third passage portion 55, which adjoins the second passage portion 50, the third passage portion 55 containing the forming tool 8. In particular, the cooling device 39 may be arranged in the second passage portion 50. According to an embodiment, a plurality of cooling devices 39 may be provided. The cooling devices 39 can be arranged in a parallel arrangement or in a serial arrangement, which is not shown in the drawing in FIG. 2.

[0046] The first cooling device 9 or the second cooling device 39 may contain a static mixer or be designed as a static mixer. In particular, the second cooling element 49 may be formed at least partially as a mixing element 41. A plurality of cooling elements 49 may be provided. The cooling element 49 or the mixing element 41 may be formed as a web element. The one or more cooling elements 49 or at least a portion of the cooling elements may include a passage through which a cooling fluid flows in operation.

[0047] The layers constituting the tube 30 may contain various plastics materials, at least a part of the layers may also contain a material which is not attributable to the group of plastics. In particular, each of the layers can be produced in a separate extruder 3, 33. For each of the layers a passage 5, 35 can be provided, by means of which the corresponding layer is transported to the forming tool 8. In particular, the layers can be guided by means of the passages 5, 35 into the forming tool 8. According to an embodiment, a plurality of annular passages 18, 38 may be provided in the forming tool 8. The annular passages 18, 38 may be merged upstream of the second end 7, 37 into a single annular passage. The forming tool 8 may include a die element, in particular an annular die. According to an embodiment, the extruder 3, 33 may be formed as a single-screw extruder.

[0048] The web elements of the first or second cooling element 19, 49 or the first or second mixing element 40, 41 may be assigned according to each of the embodiments to a first and a second web element group. The cooling device 9, 39 may comprise a first group of web elements as well as a second group of web elements. Each group may comprise a plurality of web elements. Depending on the width of the web elements and the flow passage width 1 to 100, preferably 1 to 50 web elements may belong to one group. The web elements belonging to a group can be arranged parallel to each other. The side surfaces of the web elements can be aligned in the direction of the impinging plastic melt flow and span a common plane according to an embodiment.

[0049] The web elements of the first group preferably intersect with the web elements of the second group. A web element of the first group according to this embodiment connects to a web element of the second group. The web element of the first group is thus arranged crosswise to the web element of the second group. The web elements of the first group thus alternate with the web elements of the second group. The first and second groups can each span a plane that is inclined at an inclination angle of 25 to 75 degrees to the main direction of flow. In particular, the angle may comprise 30 up to and including 60 degrees, in many cases the angle may be substantially 45 degrees.

[0050] Web elements can contain one or more channels through which a heat transfer fluid flows. The cooling device may include a pedestal or shell element that may or may not include a distribution channel for distribution of a heat transfer fluid or a collection channel for merging the heat transfer fluid from a plurality of discharge channels. For example, each of a supply channel and a discharge channel are in fluid communication with the first and second end of the rod member. For each of the web elements containing channels, at least one supply channel is provided, which supplies the heat transfer fluid to the corresponding channel in the web element and a discharge channel which directs the heat transfer fluid from the channel in the web element in a collecting channel. In this case, the heat transfer fluid is supplied and/or discharged through the tube element surrounding the plastic melt and/or the jacket of the tube element surrounding the plastic melt.

[0051] The channels extending in the web elements may have an oval or circular cross-section. The channels may also have other cross-sectional areas, for example channels with a triangular, quadrangular or polygonal, cross-sectional area.

[0052] It will be apparent to those skilled in the art that many other modifications are possible in addition to the described embodiments without departing from the inventive concept. For example, a static mixer according to EP 2851118 B1 can be used. The object of the invention is thus not limited by the foregoing description and is determined by the scope of protection defined by the claims. The widest possible reading of the claims is decisive for the interpretation of the claims or the description. In particular, the terms contain, comprise or include are to be interpreted as referring to elements, components or steps in a non-exclusive sense, to indicate that the elements, components or steps may be present or used can be combined with other elements, components or steps that are not explicitly mentioned. If the claims refer to an element or component from a group which may consist of A, B, C, N elements or components, that formulation should be interpreted as requiring only a single element of that group, not a combination of A and N, B and N or any other combination of two or more elements or components of this group.